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The involvement of the head and neck can occur in 25 to 45% of patients with burn injuries. Unfortunately, scalp burns can result in significant burn alopecia. The management of these problems depends on the location and extent of the alopecia. Tissue expansion has become an important part of the armamentarium for correction of this problem with acceptable complication rates. The results of correction of burn alopecia with tissue expansion are an important part of our surgical strategy in the aesthetic reconstruction of cicatricial alopecia.
In soft tissue injuries in patients with large total body surface burns, involvement of the head and neck can range from 25 to 45%.1,2 The human skin does not heal through tissue regeneration. Scarring is the normal end result of any traumatic injury to the skin. Burn injury only represents a segment of traumatic injuries in which scarring may become problematic. Scarring can limit function and can be aesthetically disfiguring. The long-term effect of burns to the scalp is cicatricial alopecia. The management of this problem depends on size of the defect, its location, and the status of the remaining scalp. The scalp has been a popular donor site for coverage of patients with large total body surface area (TBSA) burns. However, controversy exists as to the incidence of complications associated with graft harvesting. Brou et al reported a 61% incidence of alopecia in patients with existing scalp burns in which skin grafts were subsequently harvested for wound closure. However, only a 2.2% incidence of alopecia is noted in patients without burns to the scalp who underwent harvesting of scalp grafts for closure of burn wounds.3
The extensive use of skin grafts, local skin flaps, distant flaps, and microvascular free tissue transfer has given reconstructive surgeons significant tools in the reconstruction of burn patients. However, inherent in each of these techniques are problems with color match and texture. In addition, donor site disfigurement may also play a role both psychologically and physically. Skin expansion is based on the dynamic nature by which living tissue responds to mechanical stress. Controlled soft tissue expansion offers many advantages over other modalities in the reconstruction of burn patients. The color and texture of expanded skin is a better match to the surrounding tissues than skin grafts or even distant flaps. Donor site morbidity is minimized or eliminated. Lastly, expanded skin can maintain sensibility. Although tissue expansion has numerous advantages, it is not recommended in all situations. Yet, it is such a valuable technique that it has become an integral part of the armamentarium in the reconstruction of burn patients.
As noted, the concept of tissue expansion has occurred under both natural conditions (i.e., pregnancy and breast development) and abnormal circumstances (i.e., tumor growth). As part of the exotic aesthetics of various cultures, tissue expansion has long been noted as a method to document the positions of social hierarchy.4,5 The first clinical case of pure soft tissue expansion was reported by Neumann when he reconstructed the upper two-thirds of the right ear in a 52-year-old man by inserting a rubber balloon above the ear. This expanded flap was then advanced to cover the cartilaginous framework. However, the concept of soft tissue expansion to correct traumatic defects did not become popular for another 20 years. In 1975, both Radovan and Austad’s group began pioneering work on soft tissue expansion.6,7 Experimental data on the biology of tissue expansion has largely come from animal data. Although it is clear that Radovan became the first surgeon to gain extensive experience with tissue expanders, Austad and colleagues first reported the laboratory experience with expanders prior to clinical use.7,8 Several studies have been performed to delineate some of the histological changes that occur in expanded skin.
Initial studies of the epidermis revealed several interesting findings. Examination of tissues in both guinea pigs and humans revealed epidermal thickening.7,8,9 Further studies by Paysk et al showed that epidermal thickening persisted for 2 years after expansion.10 Interestingly enough, there was no correlation of epidermal thickening with expansion time, volume, location, or patient age. Paysk et al also showed that the epidermal thickening appeared to occur in the stratum spongiosum.10 Light microscopy revealed several interesting findings. The basal lamina appeared undulated. The tonofilaments in the basal and prickle cells revealed increased bundles of tonofibrils. These findings, along with the decrease in the intracellular spaces noted in all epidermal layers, suggested increased mitotic activity. Later, Austad et al quantitatively documented epidermal mitotic activity using tritiated thymidine.8 He noted that epidermal mitosis increased threefold during inflation but returned to baseline over the next 2 to 5 days.
The expansile and recoil properties of the skin are related to the amount of collagen and elastic fibers in the dermis.11,12 Unlike the epidermis, the dermis undergoes significant changes during the expansion process. The thickness of the dermis is reduced dramatically. Again, this is not related to expander volume or anatomic location.9 Most of the dermal thinning occurs in the reticular dermis. Although thinning of the papillary dermis is noted, this is less dramatic. During the first few weeks of expansion, the dermis thins significantly but less so toward the end of expansion process. After expansion, the reticular dermis is noted to have increased amounts of thick bundles of collagen fibers parallel to the skin. In addition, the elastic fibers in the expanded dermis were thicker and longer. It is believed that the presence of increased numbers of active fibroblasts in the dermis is responsible for the immature collagen fibers. Collagen bundles populate both the reticular and papillary dermis from the multiplication of fibroblasts.11,12
Skin has the ability to stretch and recoil. Elastic fibers, linked to each other by end-to-side junctions, are interspersed among collagen fibers, which are often larger and unlinked to another. Elastin fibers, unlike collagen, have the ability to stretch and retract. Collagen fibers in their relaxed state are disoriented and unparalleled. These fibers, in the presence of applied stress, align in a parallel fashion.9 This response is linearly proportional to the magnitude of the applied stress. In the presence of excess stress, striae formation is inevitable. In addition, too much stress during expansion of skin can cause constriction in the tiny blood vessels inducing ischemia. Our goal is to take advantage of this regenerative process without causing flap loss secondary to necrosis. It should be noted that hair follicles, sebaceous and sweat glands, and sensory nerves might undergo subtle changes, if any at all. Hair follicles and glandular tissues remain unchanged qualitatively but remain active. The lumens of various glands remain open even though adjacent structures have been compressed.11,12 In addition, sensory fibers do not undergo any appreciable structural changes.9
Fat appears to be the most intolerant of tissues to expansion. There is a marked decrease in the thickness of the adipose layer.9,11 The adipocytes became flattened and smaller. Experimental data noted replacement of adipocytes with fibrous tissue. Although frank fat necrosis has not been observed experimentally, the loss of fatty tissue appears to be permanent.
Numerous investigators have noted a significant proliferation of blood vessels associated with tissue expansion. This proliferation occurs primarily at the junction of the capsule and host tissues. Within days of expansion, small capillaries become distended, and the number of arterioles and venules increase. Cherry et al noted an increase in the surviving length of expanded random-patterned skin flaps when compared with delayed skin flaps.13 Sasaki et al later confirmed previous studies by documenting increased blood flow in expanded flaps.14 Lantieri et al later suggested that vascular endothelial growth factor (VEGF) might play a part in the development of the increased vascularity of expanded flaps as VEGF was only expressed in expanded flap.15
Initial studies by several investigations documented an increased mitotic index in the epidermal layer of the skin with expansion.7,16 Takei et al felt that several growth factors were involved in this strain-induced cellular activity.17 The process of expansion is believed to not only affect adjacent tissue but also several cell types. This group postulated that platelet-denied group factors as well as other growth factors could stimulate cutaneous cells. Although it is well known that transforming growth factor-β can influence extracellular matrix production, this growth factor can also enhance fibroblast proliferation. Lastly, membrane bound molecules may also play a role in the regulation of intercellular signal transduction pathways (Fig. 1). However, the exact mechanism by which strain influences skin biology is still unclear. Whether or not we can modulate this response chemically remains to be seen.
Correction of burn deformities using tissue expansion is a multistage process. Not only is patient selection crucial, so is individualized preoperative planning. The expectations of the patient and those of the surgeon should match. Patient acceptance of the weekly or biweekly injection processes and the progressive deformity cause by the expander is essential. Several parameters must be considered prior to expansion. Issues related to the insertion process are less controversial when compared with the details as to how this should be done. Most surgeons feel that the use of perioperative antibiotics is crucial. However, other issues are controversial. The type of incision, paralesional or remote, is still under scrutiny. The orientation and the number of expanders have also been scrutinized. What size expander should one use and how much flap advancement can be expected? These are still debated issues. Internal versus external port placement may be individualized based on circumstances. How this affects the success of expansion is not always clear.
The type of incision used to insert a tissue expander is still an issue. Clearly, healing of the incision is crucial to the initiation of the expansion process. One issue that does not appear to be controversial is size: regardless of the type of incision used, it should be as small as possible. Proponents of paralesional incisions (i.e., incisions at the junction of normal tissue and the scarred area) believe that minimal undermining of tissues is required for insertion of expanders. In addition, no statistically sound data has proven that infection rates, wound dehiscence rates, and implant exposure rates are significantly different. Proponents of the remote incision believe that healthy tissue approximated to healthy tissue affords better healing. In addition, the migration of expanders during the expansion process will not interfere with the weakest point in the skin, the incision. Complication rates have been cited to be less. However, several factors may influence this data. Currently no controlled, randomized studies exist on site-specific expansion to settle this controversy. Complications may simply be related to the quality and quantity of tissues undergoing expansion and the donor site location.
Tissue expanders come in all shapes and sizes. They can be bought “off the rack” or custom made. The choices of remote versus in situ ports are also available. In addition, differential expanders are also currently utilized. In 1984 Gibney recommended the use of expanders with a base width that is 2.5 to 3 times the width of the defect to be covered.18 Later, Manders et al recommended the use of as large an expander as possible.19 Brobmann and Huber in an experimental study on pigs addressed the issue of expander size and shape relative to the amount of expansion obtained. It was determined that less time, pressure, and volume are needed in a larger expander to achieve gain in the same surface area when compared with smaller implants.20 Several investigators have proposed the use of a mathematical model for determining the size, amount of inflation required, and expected advancement.21,22 Although this sophisticated model is mathematically sound, its complexity has not led to widespread use. When expanders are placed over rigid flat surfaces, predicting the amount of flap advancement is straightforward. It is only when expanders are placed over soft tissues with the tendency toward inward compression (i.e., the abdomen) or in areas of concavity (i.e., the neck) that the prediction of advancement is less reliable. Nevertheless, the use of as large an expander as the donor site will accept is reasonable. In the scalp, prediction of flap advancement is reliable. In the author’s experience, measuring the dome of the expander and subtracting the width of the expander is fairly accurate in determining the amount of flap advancement (Fig. 2).
Several investigators have documented safety in the use of external ports.23,24,25 Although individual circumstances and location are the best determinants as to how the port is placed, issues of safety and efficiency are not abandoned by either technique. In the pediatric population, the use of external ports can alleviate pain and anxiety associated with weekly injections.26
The rate at which expansion occurs postoperatively varies. Expansion has been recommended anywhere from 1 week to 2½ weeks after placement. Injection fractions vary, but 10% of the volume per week is required to complete expansion within a 3-month period. However, individual variations exist and one must be aware of pressure changes that occur with expansion so that flap ischemia and subsequent exposure of the expander do not become problems. Pietila et al addressed the issue of accelerated expansion with the “overfilling” technique.27 This group defined overexpansion as expansion to the point where dermal capillary flow is zero by laser Doppler flow meter and patient discomfort is high. Reportedly, fluid was then removed until capillary refill returned and the patient no longer experienced discomfort. In a series of 14 patients, they confirmed an average increase of 59% using this technique. However, complications in these patients were not addressed.
In most cases, expanders are either placed below the galea or at the fascial layer, depending on location. Meticulous hemostasis is crucial. Irrigation of the expander packet with antibiotic solution is also a common practice. Checking the expander for leakage is an important part of the procedure. The injection of air with the submersion of the expander in saline is reliable for detecting leaks. Alternatively, the use of methylene blue helps to identify expander leaks prior to insertion.28
Once the expander has been successfully inflated and ready for removal, advancement or rotation of the flap has usually been decided. Hudson feels that the best method for maximizing the use of expanded tissue in both a vertical and horizontal direction is to add back cuts to the sides as well as the base of the flap.29 Scoring the capsule to increase flap advancement has been touted by several authors. However, limitations exist. It is unclear as to the absolute increase in flap advancement gained with scoring. In addition, increased bleeding and potential damage to the overlying blood vessels may cause vascular compromise.
Radovan ushered in a new era of reconstruction in 1976, when he first placed a tissue expander in the arm of a patient to resurface a 77-cm2 defect.6 In 1984, Manders et al reported success with scalp expansion resurfacing areas of burn alopecia in children.19 Later, Manders et al reported a larger series of 35 patients undergoing 41 expansions for a wide spectrum of problems.30 Here complications associated with expansion were addressed and separated into minor complications and major complications. Major complications were defined as those that interrupted the expansion process and prevented achievement of the desired results. Marks et al reported one of the earlier series of patients with burns only who were treated with tissue expansion.31 In this series of 45 patients with burns, expanders were used to reconstruct areas of the head and neck, trunk, and extremities. This group concluded that tissue expansion was a valuable technique for correction of small and moderate-sized burn scars, if surrounded by normal tissue. It was also felt that in the head and neck region, larger defects could be addressed. MacLennon et al later reviewed their experience with expansion in the head and neck region in burn patients.32 Although results were uniformly encouraging, caution was expressed in the use of expanders to resurface the lower face and cheeks because of the risk for the development of ectropions of the eyelids and lips. Most recently, Pitanguy et al addressed the issue of repeated expansion in burn patients. Between 1985 and 2000, 346 expanders were used in 132 patients.5 In 42 of these patients repeated expansions were performed. Although complication rates were low, two points were brought to light. First, repeated expansions required an interval of 6 months to 1 year. Second, the area of reexpansion should be prepared with dermotomy, a mechanical massage method that consists of positive pressure rolling in conjunction with applied suction to the skin and subcutaneous tissues. Although this technique has not gained widespread utilization, Pitanguy et al believe that it increases vascularization and elasticity of the skin targeted for reexpansion.
Prior to expansion, burn alopecia was managed with serial excision and local flaps. Huang et al reported a series of patients with varying degrees of burn alopecia managed with serial incision.33 This group classified the extent of burn alopecia in children in an attempt to not only guide our surgical interventions but to also give us some expectations as to what to tell our patients.
Patients classified as group A had alopecia that was less than 15% of the hair-bearing scalp; in group B, the alopecia exceeded 15% but was less than 30% of the hair-bearing scalp; in group C, the alopecia exceeded 30% but was less than 50% of the hair-bearing scalp; and in group D, the alopecia was more than 50% of the scalp. Using this classification system, scar excision is possible to remove alopecia segments up to 15% of the hair-bearing scalp. Currently, if complete excision of the alopecia segment can be performed in no more than three operations, this approach is still preferred by many surgeons. If more operations are deemed necessary, alternative approaches are available.
The next stage of evolution of the closure of scalp defects came from Orticochea.26,34 The three- and four-limb Orticochea flaps were successfully used to close scalp defects greater than 15% of the hair-bearing scalp. The Juri flap, the lateral pedicled scalp flap, was described to reconstruct the anterior hairline in bald patients.35,36 Its use in combination with tissue expansion has also been described.37 However, tissue expansion has added an entirely new dimension to the treatment of burn alopecia. Presently, it may be the gold standard by which other techniques may be measured.
Many investigators have demonstrated the safety and efficiency of tissue expansion in the correction of burn alopecia.19,38,39 McCauley et al classified based both the pattern of alopecia and the extent of alopecia.38 This classification system was designed as a template by which reconstruction efforts could be designed to address specific problems with burn alopecia (Table 1). Patients with type 1A or 1B burn alopecia can be corrected with a single expansion, although overinflation may be necessary. Patients with type 1C and 1D burn alopecia may require multiple expanders either together and/or sequentially to correct these large areas of alopecia (Figs. 3, ,4).4). Patients with type IIA or IIB alopecia may also be corrected with single expansion. However, patients with type IIC and IID alopecia require intricate flap designs to correct the problem. It is important to note that scalp expansion only allows redistribution of a healthy scalp tissue without creating new hair follicles. It has been noted that the interfollicular distance can increase twofold without noticeable thinning of the hair.30 Several investigators have been reluctant to address burn alopecia greater than 50% of the hair-bearing scalp, citing poor results. However, alternatives to resurfacing of the scalp are limited and some patients feel that some hair is better than no hair (Fig. 5).
Reports of complications in the use of tissue expansion are numerous. In 1984, Manders et al detailed their experience with 41 expanders in 35 patients as a multisite review.30 They defined complications as major or minor. Major complications of expansion were those that interrupted the expansion process (Table 2). Minor complications were defined as problems that were resolved without failure of the procedure (Table 3). In this review, 25% of patients had major complications requiring alterations in the treatment plan and 17% had minor problems. Zellweger and Künzi had similar problems with 5 of 21 patients requiring premature removal of the expander (22%).40 Governa et al documented their experience in 157 patients with 262 expanders.41 Complete resurfacing of the intended area, however, was obtained in only 62% of the patients. Complications occurred in 27.9% of the expanders. However, 41% of these problems could not be solved and may be classified as major complications (12.6%). Although it is important to note expander complications, the number of patients who experience major complications is more important. This study alludes to only 10 failures in 157 patients.
In a retrospective review of 346 expanders in 132 patients, Pitanquy addressed the issue of reexpansion noted in 42 patients. Although the overall complication rate was low (7.5), it is unclear as to whether repeat expansions were associated with increased complication rates.5 In 1998, Pisarski et al shed a different light on multisite expansion studies by detailing their complication rates over two separate time periods.42 Refinements in techniques, protocols, and surgeon maturity, when all sites are included, reduced complication rates from 30% to 18%. To date, it appears that the overall complication rate for tissue expansion is around 15 to 20% despite advances in techniques and strict protocol procedures.
The number of site-specific studies lends crucial insight into complications associated with expansion of different regions in the body. Scalp expansion for correction of burn alopecia is well documented.31,38,39 As noted in scalp expansion reviews, the use of tissue expanders for the correction of burn alopecia has revolutionized our thinking as to the correction of this problem.5,30,37,40,41 Of major concern, here, is flap advancement to maintain proper orientation of the hair follicles. Whether or not these wounds are drained does not seem to affect the major complication rate of 12 to 20%.
Tissue expanders have solidified their place in the armamentarium of reconstructive surgery, bringing with it new perspectives. The techniques have been refined, and although complication rates have become less, nonetheless, they remain high. The advantages of this technique are numerous: excellent color and texture match and minimal donor site morbidity. The disadvantages are well known and include a protracted time period for completion of the expansion process and a significant complication rate. All patients who are victims of trauma, especially burn injury, want to look and function at their best. Tissue expansion in certain patients offers the chance to replace unstable and unsightly scars with normal adjacent tissue. None of our current reconstructive techniques offers this advantage. As we continue to refine our approach to certain problems using tissue expansion, it’s important to communicate to our patients that although the process may be long and complicated, the end results can be exceptional. Our acceptance of the numerous problems associated with tissue expansion is a testament to the power of this unique reconstructive technique.